A client establishes a Transmission Control Protocol (TCP) connection with an Internet server through a mobile communications network. The client is connected to the mobile communications network through a wireless link, while, generally, the mobile communications network is connected to the Internet server through a wired network. A time-variant characteristic of wireless links is obvious, and therefore, changes of a data transmission rate, a packet loss rate, and so on between the client and the mobile communications network over time are dramatic. In this case, a transmission policy is adjusted by using a TCP congestion control method for the wired network. However, because a transmission characteristic of a wireless network is different from that of a wired network, the TCP congestion control method put forward for the wired network is not quite applicable to the wireless network.
For the foregoing problem, a network proxy technology is put forward in the prior art, where a TCP connection between a client and an Internet server is divided into two parts: one part is a TCP connection established between the client and a network proxy and aiming at a wireless network, and the other part is a TCP connection established between the network proxy and the Internet server and aiming at a wired network. In this way, a TCP congestion control method applicable to the wireless network can be used between the client and the network proxy, and a conventional TCP congestion control method can be used between the network proxy and the Internet server. The existing network proxy technology may lower the quality of service of the wireless network, and therefore, a new data transmission technology is required.